Electric field spraying of surgically implantable components

ABSTRACT

This invention relates to a method for depositing a coating onto an implantable medical component using electrohydrodynamics (“EHD”). The method utilizes EHD to comminute a suitable liquid which then form fibers or particles. The thus-formed fibers or particles are electrically attracted to the medical component and coat at least one surface of the medical component. A wide-variety of liquid formulations can be utilized to deliver a wide-variety of, for example, therapeutic substances, either alone of in combination. Fiber-based and particle-based coatings may be applied as well as combinations thereof. Also disclosed are medical components comprising such coatings, particularly stents.

This application claims priority to U.S. pat. app. Ser. No. 60/504,816filed Sep. 22, 2003, the contents of which is hereby incorporated as iffully rewritten herein.

FIELD OF THE INVENTION

The present invention provides a method of applying a coating to animplantable medical component either alone or in a combination with atherapeutic substance. More specifically, the present invention relatesto electric field spray-coating of stents with therapeutic substances,wherein the stents are designed for storing and releasing thetherapeutic substances, for instance, such as those used in thetreatment of restenosis.

BACKGROUND OF THE INVENTION

When blood vessels are treated, stents are frequently used to preventvessel blockage from restenosis. Stents are well-known in the medicalarts. A stent is typically an open tubular structure that has a pattern(or patterns) of apertures extending from the outer surface of the stentto the lumen. The stent can have either solid walls or lattice-likewalls, and can be either expandable or self-expanding. A stent can bedelivered on a catheter and expanded in place or allowed to expand inplace against the vessel walls. With the stent in place, restenosis mayor may not be inhibited, but the probability and/or degree of blockageis reduced due to the structural strength of the stent opposing theinward force of any restenosis. Restenosis may occur over the length ofthe stent and be at least partially opposed by the stent. Restenosis mayalso occur past the ends of the stent, where the inward forces of thestenosis are unopposed.

To reduce or prevent the occurrence of restenosis, there are stentdesigns which incorporate a therapeutic drug (such as an anti-coagulant,immunosuppressant, or anti-inflammatory) into or onto the stent body,which drug may diffuse or be released after the placement of the stentinto a vessel. In one design, the therapeutic drug is coated onto thesurface of the stent body. As fluid flows across the surface of thestent, the coating degrades and releases the therapeutic drug from thestent.

The therapeutic drug incorporated into the stent may not be included toprevent restenosis, but rather to treat a medical condition at the siteof the stent (for example, an antineoplastic agent to treat a site wherea tumor has been removed). As the stent is designed to deliver atherapeutic drug to a local site, for example, a constriction sitecaused by restenosis, a therapeutic drug may be disposed on the outerstent wall, or the inner stent wall or within the stent wall. Tomaintain the drug within the space, the drug may be imbedded within acarrier, such as a bioabsorbable gel. The stent further may include apattern of perforation extending from the outer wall, across thethickness of the wall, and through to the inner wall. The presence ofthe perforation permits the stent to expand radially in diameter.

It is commonplace to make stents of biocompatible metallic materials,with the patterns cut on the surface with a laser machine. The stent canbe electro-polished to minimize surface irregularities since theseirregularities can trigger an adverse biological response. However,stents may still stimulate foreign body reactions that result inthrombosis or restenosis. To avoid these complications, a variety ofstent coatings and compositions have been proposed both to reduce theincidence of these complications or other complications and restoretissue function by itself or by delivering therapeutic compound to thelumen.

Stents may be coated by simple dip coating with a polymer or a polymerand pharmaceutical/therapeutic agents. Dip coating is usually the mostsuccessful for low viscosity coatings. The presence of pharmaceuticalagents in polymers usually makes the coating solutions more viscousbecause the polymers need to encapsulate the drug. Dip coating usinghigh viscosity solutions typically causes bridging, i.e., forming of afilm across the open space between structural members of the device.This bridging can interfere with the mechanical performance of thestent, such as expansion during deployment in a vessel lumen.

Implantable components such as stents can also be coated usingconventional pneumatic spray methods. However, the quality and quantityof the material deposited on the implantable component are critical andpneumatic spraying methods require especially close control of processparameters such as fluid viscosity, spray nozzle condition, materialdeposition rates, and target placement relative to the spray nozzle toname a few. Pneumatic spray coating methods can be somewhat inefficient.For example, material lost due to overspray (a function of targetcomponent geometry and nozzle placement) and requirements for continuousnozzle maintenance and high solvent concentrations (to prevent cloggingand process downtime) are key issues of concern.

During a spray coating process, micro-sized spray particles aredeposited on the stent. Particles are lost due to the atomizationprocess and this loss also results in the loss of significant amounts ofthe pharmaceutical agent(s), which can be quite costly. In order toquickly and efficiently load the stent with an optimum drug dosage, itis desirable to minimize the lost particles so that the amount of drugapplied to the stent can be readily predicted from the quantity ofmaterial delivered in the coating process.

Several bonding techniques, such as anionic bonding and cationicbonding, can also be used for attaching the polymers and theencapsulated polymers on the surface of the stent. During the ionicbonding process, the polymer is applied to the surface where the bondingbetween the pharmaceutical agent and the polymer is a chemical mixturerather than a strong bond. In covalent bonding, the attachment of thepolymer and the pharmaceutical mixture to the surface of the stent isthrough a chemical reaction. For example, the stent is first cleanedwith a primer that leaves a hydroxyl-terminated group on the surface ofthe stent. This hydroxyl-terminated group attaches itself to the polymerchain, which in turn contains the pharmaceutical compound chemicallyattached to it.

It is known to utilize electrostatic spray deposition (ESD) to applybiocompatible coatings onto an implant for implantation in bone. Forexample, EP Pat. Pub. 1 275 442 to Jansen et al., published Jan. 15,2003, teaches forcing a precursor solution comprising inorganics such ascalcium and phosphate through a capillary which is subjected to anelectrical field. The coating, then, enhances the attachment of bonecells to the implant.

It is also known to utilize the application of an electrical chargedirectly to the material being sprayed to coat medical devices such asstents. U.S. Pat. Pub. No. 2003/0054090 to Hansen, published Mar. 20,2003 (“Hansen”), for example, teaches the use of a nozzle made of aninsulative material to enable the material to be sprayed to be chargeddirectly. As a result of the repulsive force of the electrostaticcharge, the material is forced out of the nozzle. Hansen also teachesstrictly applying a coating from the outside of the device or stent.Thus, it can be difficult to achieve an adequate and uniform coatingover the entire surface of the device since the outer surfaceeffectively shields the inner surface from the effects of theelectrostatic charge.

Thus, there exists a need for an apparatus and method for coatingmedical devices, particularly stents, which does not cause the bridgingassociated with dip coatings, provides a more efficient spraying whichdoes not result in the overspray and waste of material associated withpneumatic spraying, and which can effectively provide even, uniformcoverage over the entire surface of the device.

BRIEF DESCRIPTION OF THE INVENTION

It is thus an object of the present invention to provide a method forcoating an implantable medical component using EHD techniques to form acoating on a surface of the component comprised substantially of fibers.It is a further object of the invention to provide a coating wherein thecoating comprises at least one therapeutic substance. It is yet afurther object of the invention utilize a solvent which substantiallyevaporates prior to the coating being formed. It is yet a further objectof the invention to provide a melted polymer to an EHD device whichtechniques then form a coating on a surface of an implantable medicalcomponent.

It is another object of the invention to provide a method for coating aninterior surface of an implantable-medical component using a EHD-basednozzle-positioned within the interior of the medical component. It isyet a further object of the invention to move the nozzle relative to themedical component along a path through at least a portion of the medicalcomponent.

It is yet another object of the invention to provide a method forcoating an implantable medical component using a non-conducting mandrelhaving a first potential and using EHD techniques to form a coating on asurface of the component. It is yet a further object of the invention toeffect the first potential with a reference electrode.

It is yet another object of the invention to provide a method forcoating an implantable medical component using EHD technology to coat anexterior surface of the medical component with a first material andusing EHD technology to coat an interior surface of the medicalcomponent. It is yet a further object of the invention to provide amethod for coating an implantable medical component with a combinationof fibers and particles.

It is yet another object of the invention to provide implantable medicalcomponents coated with the aforementioned EHD techniques. It is yet afurther object of the invention to provide stents coated with theaforementioned EHD techniques.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a typical EHD spray configuration.

FIG. 2 illustrates an alternative EHD spray configuration.

FIG. 3 illustrates another alternative EHD spray configuration.

FIG. 4 illustrates the use of EHD to coat an inside surface of acomponent such as a stent.

FIG. 5 illustrates the use of EHD to spray fibers onto a component suchas a stent.

DETAILED DESCRIPTION OF THE INVENTION

Significant improvements to the process of stent (medical component)coating can be realized by delivering the coating material via electricfield spraying, specifically electrohydrodynamic (“EHD”) dropletgeneration, whereby the formulation is delivered to a spray site whereit is exposed to an electric field and forms a so-called cone-jetconfiguration to produce highly-charged, micron-sized droplets havingnearly uniform size. The term “EHD spray” as used herein refers to afreely divided spray of liquid droplets generated by applying anelectric field to a liquid at a spray head or spray edge. In EHD spraytechnology, the potential of the electric field is sufficiently high toovercome the surface tension of the liquid. The cone shape of the liquidat a spray site results from the electric field and surface tensionforces balancing each other. The so-called Taylor cone wasmathematically described by Geoffrey Taylor; hence, the phenomenon bearshis name. At the apex of the cone, a fine jet of the liquid forms thatsubsequently breaks up into micron (and possibly even sub-micron) sizeddroplets, fibers, or fibrils having approximately the same size andelectrical charge. A unique feature of EHD spraying is the ability toproduce a population of aerosol droplets having a controllable andnarrow size distribution. Since the charged droplets are uniformlysized, as well as dispersed by their mutual repulsion, the ability touniformly coat a surface is enhanced.

A common feature of all known EHD spray devices is that the electriccharge used to generate the spray is either applied directly to orinduced in the spray head. See, e.g., U.S. Pat. No. 6,105,571 to Coffee,issued Aug. 22, 2000, which is incorporated herein by reference. This isin contrast to electrostatic spraying, which refers to a process wherethe droplets are first formed, generally through atomization, and thenthe droplets are subsequently charged, generally using a high voltagesource, as they exit a spray head.

As used herein, the term “coating” is used in its broadest senseintending to encompass embodiments where an entire stent is coated, onlya portion of the stent is coated, a surface (e.g., inner or outer) ofthe stent is coated, a uniform coating is applied, a non-uniform coatingis applied, a layered coating is applied, a surface consists of bothcoated and non-coated areas, to name a few of the variations.

It may not be necessary to orient the surface of the target such that itis facing the spray nozzle. Depending on the size of the target anddistance to the nozzle and other considerations, the use of atranslation or rotary stage may not be necessary. This EHD process mayalso offer an opportunity for coating selected surfaces of the target(e.g., inside versus outside walls or end faces). Thus, EHD may be usedto achieve either broad surface coverage of the stent or very specificcoverage of the stent surface. For example, as a result of the electricfield dispersion and the charged particles produced, EHD spray canprovide a “wrap-around” effect which allows for the easy coasting of allstent surfaces (including difficult-to-reach locations). On the otherhand, EHD can be used to coat specific stent surfaces or specificportions of a stent surface. (For example, the interior surface can becoated with a drug which treats the blood flowing through the stent,while the outside surface can be coated with an anti-infectivematerial.)

The coating materials may contain a number of components, includingbiocompatible polymers, therapeutic substances such as those which limitrestenosis or which treat atherosclerotic plaque (e.g., blood thinnersor anti-infective agents), anti-bacterial agents, and other activeingredients designed to maintain the stability and longevity of theimplanted component after it has been surgically placed. Therapeuticsubstances include, but are not limited to, immunosuppressants such assirolimus, chemotherapeutics such as paclitaxel, antineoplastics such asactinomycin D, antisense compounds such as resten-NG,anti-inflammatories such as dexamethasone, metalloproteinase inhibitorssuch as batimastat, and anti-proliferative compounds, and combinationsthereof. These substances may also be incorporated into polymers fortimed-release applications of the present invention. Additionalinformation on stents, and particularly drug eluting stents can be foundat www.tctmd.com.

The therapeutic agent may be applied to the stent from a solution or asuspension. Multiple sprays may be used to apply the material ormultiple layers of material may be applied. It is even possible to havedifferent materials on the inside and the outside of the stent (forexample, a drug can be released into the bloodstream from the insidesurface of the stent, while a restenosis preventive is released from theoutside surface of the stent.

When coating an implant, a bioresorbable, biodegradable and/orbio-compatible polymer is generally used. Such polymer can be a singlepolymer, a co-polymer, or a mixture of polymers selected from the groupconsisting of, for example, polypeptides, polydepsipeptides, nyloncoployamides, aliphatic polyesters, polydihydropyrans, polyphosphazenes,poly(ortho ester), poly(cyano acrylates), poly-anhydrides, modifiedpolysaccharides and modified proteins, and mixtures thereof. Some ofthese polymers, such as polylactates, can be melted and mixed with theactive material. When delivered in this way, the spray conditions may besuch that the mixture solidifies either before or after being deliveredto the surface of the stent.

Aliphatic polyesters are, for example, selected from the groupconsisting of poly(glycolic acid), poly(lactic acid), poly(alkylenesuccinates), poly(hydroxyl-butyrate), poly(butylene diglycolate),poly(epsilon-caprolactone), copolymers, and mixtures, thereof.

Modified polysaccharides are, for example, selected from the groupconsisting of cellulose, starch-alginate and the glycosaminoglycans,chondroitin sulfate, heparin, heparin sulfate, dextran, dextran sulfate,chitin, chitosan and chitosan sulfate, and mixtures thereof.

The solvent or carrier system used will generally be aqueous-based orinclude organic solvents, such as ethanol or methylene chloride,depending on the polymer chemical structure. When the active material(with or without a polymer) is delivered from a solution or asuspension, the spray conditions may be controlled such that the solventevaporates either before or after being delivered to the surface of thestent.

When charged droplets or particles contact a target surface, theelectrical charge enhances their adhesion. Since the droplets are notimmediately discharged, additional droplets directed toward the targetare repelled to areas that have fewer droplets and hence less charge.This effect can yield a high degree of uniformity of the coating on thetarget surface.

FIG. 1 illustrates a typical EHD spray configuration. As shown, acomposition to be sprayed 50 is introduced to spray tube 10. A highvoltage source 40 is connected to the spray tube 10. A target component20 is connected to an earth ground 30. In operation, the composition 50forms a Taylor cone 60 at the exit of the spray tube 10 which becomes ajet 65 and the jet produces a spray 70 which carries a electric charge.

FIG. 2 illustrates an alternative configuration. For some small targetcomponents 120, there are advantages to charging a target 120 andgrounding a spray tube 110.

When the spray tube 110 is grounded (FIG. 2), the difference inelectrical potential between the spray tube 110 and the fluid reservoir(not shown) is eliminated and the pump and associated plumbing (notshown), are typically at earth potential. With all components associatedwith a composition 150 at the same potential, there is no need toprovide insulation or other means of electrical isolation, as therewould be in the configuration shown in FIG. 1. Although not shown, aseries resistance may be placed in the conductor attached to the target120 to control the rate of the charge dissipation of the target 120.This element, combined with the rate of liquid delivery, can control theamount and deposition uniformity of material coating the target 120.

While FIGS. 1 and 2 illustrate that a direct electrical contact to thetarget 20, 120 is made in order to establish a complete electriccircuit, this configuration is not necessary. FIG. 3 illustrates atarget 220 can be held on a mandrel 280 or other suitable holdingfixture. The mandrel 280 can be conducting or non-conducting. If themandrel 280 is conducting, the system configuration is similar to thatof FIGS. 1 or 2. If it is non-conducting, however, a separate referenceelectrode 290 is required. In FIG. 3, the reference electrode 290 is onthe axis of and through the mandrel 280. If the reference electrode 290extends through the entire length of the target 220, a capacitiverelationship exists that places the target 220 at a potential that isclose to (but not exactly at) the potential of the reference electrode290. Therefore, a strong electric field gradient will exist between thetarget 220 and the spray tube 210, allowing EHD spraying to occur.

In addition to eliminating the need to directly electrically connect tothe target, this geometry has the additional feature of greateruniformity of coating of the sprayed composition 250 to the surface ofthe target 220. As the charged material 270 strikes and adheres to thetarget 220, it is not readily discharged by the reference potential. Infact, if the mandrel 280 is comprised of low leakage dielectricmaterial, the target 220 will begin to charge at a potential thatapproaches that of the spray tube 210. When this occurs, less of thecharged material 270 will be attracted to the target 220, especially inareas of highest droplet/charge density; hence, this built-in feedbackmechanism can control the uniformity and the amount of sprayedcomposition 250 applied to the target 220. This process is also valid ifthe surface of the target is non-conducting.

If the target 220 is metallic or otherwise electrically conducting,greater control over the delivery process can be gained by fabricatingthe mandrel 280 from resistive or-semi-conducting-material.Deposited-charged material 270 will eventually be discharged through themandrel 280, but the rate of discharge can be controlled by theconductivity of the mandrel/holding fixture. When this discharge rate iscoupled to the fluid flow rate, the amount of deposited sprayedcomposition 250 can be very precisely controlled while maintaininguniform deposition.

A further feature of the invention is the use of non-conducting holdingfixtures/mandrels 280 and other non-conducting shields (not shown) todirect the charged material 270 toward the conducting target 220.Laboratory experiments have demonstrated that the non-conductingsurfaces will initially receive a minimal amount of charged material,but since the material 270 cannot be readily discharged, additionaldroplets are diverted from the dielectric shields and/or the dielectricmandrel/holding fixture 280 and toward the target 220. This maximizesthe amount of material 250 that is deposited onto the target 220.

As shown in FIG. 4, it is also possible to coat an internal surface of atarget 320. This makes it possible to have different coatings on theinternal and external surface of the target. Ideally, the spray tube 310should be made of non-conducting material, including, but not limitedto, suitable polymers or ceramics, to minimize the opportunity of arcingor electrically shorting from the spray tube 310 to the target 320. Forthis configuration, the composition to be sprayed 350 itself is chargedto a high voltage substantially upstream from the site where the Taylorcone 360 is formed. Alternatively, the target 320 may be charged to ahigh potential, while the composition 350 is earth grounded.

EHD techniques may also be used to electrically spin fibers and thesefibers may also be used to form a coating for the medical components ofthe present invention. As shown in FIG. 5, EHD spinning involves theintroduction of material 450 into an electric field, whereby thematerial 450 is caused to produce fibers 470, which tend to be drawn toan electrode. While being drawn from the material 450, the fibers 420usually harden, which may involve mere cooling (e.g., where the material450 is normally solid at room temperature), chemical hardening (e.g., bytreatment with a hardening vapor) or evaporation of solvent (e.g., bydehydration). Alternatively, the product fibers 470 may be collected ona suitably located receiver (not shown) and subsequently stripped fromit. The fibers 470 obtained by the electrostatic spinning process may bethin, of the order of 0.1 to 25 microns, preferably 0.5 to 10 micronsand more preferably 1.0 to 5 microns in diameter. See, e.g., U.S. Pat.No. 4,043,331 to Martin et al., issued Aug. 23, 1977, the contents ofwhich are herein incorporated by reference.

Accordingly, instead of the jet breaking up into droplets, it remainscontiguous and forms a fiber 470 (FIG. 5) that, over a period of time,will produce a non-woven matrix of fibers on the surface of the target420. In the case of stents and similar porous structures, these fibers470 can provide a secondary mesh that has mechanical resilience andflexibility, as well as the ability to contain and release an activeingredient to its environment. A fiber matrix on the stent may allow thestent to be flexible for placement, yet have a fine enough mesh toprevent tissue infusion into the stent.

1. A method for coating an implantable medical component, comprising: a.providing a medical component; b. using EHD techniques to form chargedfibers; and c. forming a coating comprised substantially of the fiberson a surface of the medical component.
 2. The method of claim 1, whereinthe coating comprises at least one therapeutic substance.
 3. The methodof claim 2, wherein at least a portion of the medical component includesa foraminous surface, and the step of forming a coating includes forminga web of fibers over at least a portion of the foraminous surface. 4.The method of claim 2, wherein the step of forming a coating includesthe step of forming a fibrous mat which defines an upper surface area ofa medical device.
 5. The method of claim 2, wherein the medicalcomponent comprises a stent and the step of forming a coating includesforming a web of fibers over at least a portion of the stent.
 6. Themethod of claim 1, wherein the charged fibers further comprise a solventthat substantially evaporates prior to forming the coating on thesurface.
 7. The method of claim 2, wherein the charged fibers furthercomprise a solvent and the solvent substantially evaporates before thetherapeutic substance is deposited onto the surface of the medicalcomponent.
 8. The method of claim 4, wherein the charged fibers furthercomprise a solvent and the solvent substantially evaporates after thetherapeutic substance is deposited onto the surface of the medicalcomponent.
 9. The method of claim 1, wherein the step of using EHDincludes providing melted polymer to an EHD device.
 10. The method ofclaim 7, wherein the coating comprises a polymer material comprising apolylactate.
 11. The method of claim 9, wherein the step of forming acoating includes substantially solidifying the fibers and depositing thefibers onto the surface of the medical component.
 12. The method ofclaim 9, wherein the step of forming a coating includes depositing thefibers and substantially solidifying the fibers after depositing thefibers onto the surface of the medical component.
 13. A method forcoating an interior surface of an implantable medical componentcomprising the steps of: a. supplying a liquid to at least one nozzle;b. positioning the at least one nozzle within the interior of themedical component; and c. subjecting the nozzle to an electric field,thereby causing the liquid to form at least one electrically-chargedTaylor cone which forms at least one electrically-charged jet, andwherein the at least one electrically-charged jet comminutes to formcharged material which deposits onto the interior surface.
 14. Themethod of step 13, wherein the material comprises particles.
 15. Themethod of step 13, wherein the material comprises fibers.
 16. The methodof claim 13, further comprising the step of: d. moving the nozzlerelative to the medical component along a path through at least aportion of the medical component.
 17. The method of claim 16, whereinthe medical component comprises a stent, and at least a portion of thepath of the nozzle is generally axially through a portion of the stent.18. A method for coating an implantable medical component comprising thesteps of: a. supporting the component on a non-conducting mandrel havinga first electrical potential; b. supplying a liquid to a least onenozzle; and c. subjecting the nozzle to a second electrical potential,causing the liquid to form at least one electrically-charged Taylor conewhich forms at least one electrically-charged jet, comminuting the atleast one jet, and forming charged material; and d. depositing thecharged material onto a surface of the medical component.
 19. The methodof claim 18, wherein the first electrical potential is effected by areference electrode.
 20. A method for coating an implantable medicalcomponent comprising the steps of: a. supplying a liquid comprising asolvent to at least one nozzle; b. subjecting the nozzle to an electricfield, thereby causing the liquid to form at least oneelectrically-charged Taylor cone which forms at least oneelectrically-charged jet, wherein the at least one electrically-chargedjet comminutes to form charged material which deposits onto a surface ofthe medical component, and wherein the conditions are such that thesolvent substantially evaporates before the therapeutic substance isdeposited onto the surface of the medical component.
 21. A method forcoating an implantable medical component comprising the steps of: a.providing a non-conducting mandrel having an electrode disposed therein;b. electrically isolating and supporting the medical component on thenon-conducting component; c. inducing, with the electrode, an electricalpotential in the medical component; and d. using EHD to form a chargedmaterial and depositing at least a portion of the charged material ontoan exterior surface of the medical component.
 22. The method of claim21, wherein the charged material is at least partially discharged priorto deposition on the exterior surface.
 23. A method for coating animplantable medical component comprising the steps of: a. supporting thecomponent on a non-conducting mandrel having a first electricalpotential; b. supplying a liquid to at least one nozzle; c. using EHD toform a first charged material and depositing at least a portion of thefirst charged material onto an exterior surface of the medicalcomponent; d. removing the mandrel from the medical component; e.supplying a liquid to at least one nozzle positioned at least in partwithin the interior of the medical component; and f. using EHD to form asecond charged material and depositing at least a portion of the secondcharged material onto an interior surface of the medical component. 24.The method of claim 23, wherein the step of depositing the firstmaterial comprises substantially depositing the first charged materialonto the exterior surface and the step of depositing the second materialcomprises substantially depositing the second charged material onto theinterior surface of the component.
 25. The method of claim 23, whereinthe first material comprises fibers.
 26. The method of claim 25, whereinthe second material comprises fibers.
 27. The method of claim 25,wherein the second material comprises particles.
 28. The method of claim23, wherein the first material comprises particles.
 29. The method ofclaim 28, wherein the second material comprises fibers.
 30. The methodof claim 27, wherein the second material comprises particles.
 31. Amethod for coating an implantable medical component comprising the stepsof: a. supplying a first liquid to at least one first nozzle; b.subjecting the first liquid to an electric field, thereby causing thefirst liquid to form at least one electrically-charged first Taylor conewhich forms at least one electrically-charged first jet, and wherein theat least one first jet comminutes to form first charged fibers whichsubstantially deposit onto a first surface of the medical component; c.supplying a second liquid to at least one second nozzle; and d.subjecting the second liquid to an electric field, thereby causing thesecond liquid to form at least one electrically-charged second Taylorcone which forms at least one electrically-charged second jet, andwherein the at least one second jet comminutes to form second chargedfibers which substantially deposit onto a second surface of the medicalcomponent.
 32. An implantable medical component comprising a coatingapplied by the method of claim
 1. 33. A stent comprising a coatingapplied by the method of claim
 2. 34. A implantable medical componentcomprising a coating applied by the method of claim
 13. 35. A stentcomprising a interior coating applied by the method of claim 13 and aexterior coating applied by the method of claim
 1. 36. A stentcomprising a coating applied by the method of claim 27.